Field
The present application relates generally to a system and method for deep sea generation and/or storage of the products of water electrolysis and/or electric power.
Description of the Related Art
The current state of the art in geothermal production of electricity utilizes the heat in geothermal reservoirs of hot water or steam found under the surface of the land. However, the accessible geothermal resource base in the United States that is useable in current methods of generation is not sufficient to solve the current major issues in the electric generating industry such as global warming, pollution, or the costs and risks inherent in reliance on fossil fuels or in disposing of nuclear wastes.
Meeting tomorrow's needs by satisfying the increasing demand for electricity while enabling the retirement of less desirable modes of generating electricity such as the burning of coal or oil can require much more geothermal energy than is available using existing geothermal technology. Fortunately, the amount of geothermal heat available is far greater than the geothermal resource base that is accessible using current methods. Professor Jefferson Tester of the Massachusetts Institute of Technology has estimated that approximately 100 million quads of geothermal energy could be harvested per year. See, K. Bullis, “Abundant Power from Universal Geothermal Energy,” MIT Technology Review, Aug. 1, 2006. The California Energy Commission has estimated that the geothermal heat contained in just the top six miles of the Earth's mantle represents 50,000 times as much energy as the combined reserves of oil and gas in the world.
Electricity produced from geothermal resources using current technology is almost cost competitive with energy produced from fossil fuels. (The average cost of electricity produced by binary geothermal plants is 5 cents to 8 cents per kilowatt/hour according to the National Renewable Energy Laboratory, “Geothermal Technology Program” at http://www.nrel.gov/geothermal/geoelectricity.html.) The current geothermal generating technology does not, however, operate at the temperatures or the efficiency of fossil-fueled plants.
As generating stations are developed and deployed, they are expected to gradually replace the fossil-fueled power plants that provide most of the electricity for the grid. It is, however, clear that petroleum and other current forms of transportation fuels will also have to be replaced in order to stop and reverse global warming. It is not yet clear whether it is electricity or hydrogen that will be the successor to such transportation fuels; in fact, both electricity and hydrogen may be so used at the same time, in different instances. In either event, electricity and hydrogen are means of storing and transporting energy, rather than sources of energy; the ultimate goal is to replace petroleum with geothermal energy as the source of energy for transportation. If electricity is the successor, then the demand for transportation energy can be met by the generating station, with base load electricity being put into bulk storage during off-peak hours. If the successor is hydrogen, the generating station operating in conjunction with electrolysers may meet the demand for fuel.
The current state of the art in the production of hydrogen uses chemical reactions to remove the hydrogen from hydrocarbons. This approach not only consumes some of the limited and increasingly expensive hydrocarbon fuels, it increases global warming. An alternative method of producing hydrogen uses electrolysis, but this method is too inefficient, and therefore too expensive, to be economically competitive. If, however, the generating stations produce direct current, as discussed below, they are expected to make alkaline electrolysers more efficient. Moreover, current research and development is progressing on high-temperature (or “steam”) electrolysis, which is expected to become even more efficient. See Sigurvinsson, J., C. Mansilla, P. Lovera, and F. Werkoff, “Can High Temperature Steam Electrolysis Function With Geothermal Heat?” 32 International Journal of Hydrogen Energy, 2007 (pp. 1174-1182).
Currently, the energy industry is divided into the production of fuels for transportation and other purposes, and the production of electricity for the grid. The industry for transportation fuels is almost entirely separate in its operations from the electricity industry. The electricity industry is designed to be able to adjust production immediately to the grid's demand at any point in time, using some base load production and some “peaking” production, because storage of electricity is relatively expensive. Production of transportation fuels, however, is maintained at relatively constant levels, and substantial inventories of fuel are created and subsequently used as needed.